With the ZigBee protocol officially approved in the first quarter of 2005, Microchip's PICDEMô Z ZigBee demonstration kit provides a timely means of starting a new design. The kit includes two motherboards, two 2.4 GHz RF cards, and a CD containing the ZigBee protocol software and a PCB layout database. In addition, the kit includes protocol stack hardware that is preloaded into the MCUs, demonstration software (preloaded), and even the batteries. That is essentially everything an engineer needs to establish a simple point-to-point network for first-hand ZigBee experience. The kit includes an application note providing detailed "how to" and insight into the ZigBee software stack operation.
The ZigBee protocol addresses low data-rate control and monitoring applications with data rates of 250 kbps, 40 kbps, and 20 kbps for 2.4 GHz, 915 MHz, and 868 MHz channel frequencies. The specification targets low power consumption, long battery life applications that range from simple star networks to complex mesh or peer-to-peer networks. Three types of nodes are defined: Reduced Function Device (RFD), Full Function Device (FFD), and Coordinator.
Targeted for control and monitoring applications, ZigBee is a moderate to low bandwidth wireless protocol with low power consumption and low overhead so it easily runs on an 8-bit microcontroller. Building automation, industrial automation, instrumentation, and home automation are among the early adapters for ZigBee technology. In building automation, lighting heating ventilating and air condition (HVAC) control, and security provide specific examples of ZigBee applications.
Easy wireless connection: The RF daughtercard on the PIC-DEM Z demo board uses Chipcon's CC2420 2.4 GHz transceiver with an integrated printed circuit board antenna.
The MCU selected for the demo board, the PIC18LF4620, uses Microchip's Nanowatt Technology for low power management, which complements ZigBee's low power design approach. With 64 kbytes self-programmable Flash memory and 4 kbytes RAM, this unit provides sufficient application space for user's code including diagnostics and experiments. The protocol stack for the reduced function, full function, and coordinator ZigBee nodes is about 12 kbytes. Since the software stack is written in C and available under a no cost license, it is easy to understand and mate to other transceivers.
Once the true application requirements are determined, something as small as a 28-pin packaged 8-bit MCU with 32 kbytes Flash memory could be used for production. In the PIC18 family, other products provide alternative choices for memory size, peripherals, I/O, and package types.